The engagement of the inflammatory reply in diabetic rats: envolvement of mast cells and extracellular matrix components.

by Campos, Leandro Vespoli

Abstract (Summary)

The incidence of diabetes and allergic diseases is increasing worldwide every year. However, the concurrence of these pathologies in the same individual is less frequent than predicted. Based on the above observations, in this study we aimed to investigate the influence of experimental diabetes on the allergic response in dorsal skin of rats, focusing on mast cell population and extracellular matrix components. Wistar rats were turned diabetic by intravenous injection of alloxan and the analyses made 21 days later. Sensitization was performed with a mixture of ovalbumin and aluminium hydroxide, 7 days after diabetes induction, and analyses made on day 14 after the sensitization. We noted that: (1) diabetic sensitized rats exhibited less intense protein extravasation in the dorsal skin as compared to non-diabetic sensitized animals; (2) skin fragments of diabetic rats stimulated with antigen in vitro showed lower levels of histamine released than those from sensitized rats; (3) the skin from diabetic rats were less thick (about 30%) when compared to that from normal animals; (4) diabetic rats showed less density of mast cells in the dorsal skin as compared to normal animals; (5) diabetic rats showed lower expression of laminin and fibronectin in extracellular matrix presented in the dorsal skin; (6) treatment of diabetic rats with insulin significantly reversed the reduction of skin thickness, of mast cell number and of the expression of matrix proteins. In conclusion, our findings indicate that rats turned diabetic after alloxan injection were shown to be hyporesponsive to cutaneous antigen stimulation, as compared to non-diabetic sensitized ones, phenomenon which paralleled with reduction in mast cell depletion and decreased in the laminin and fibronectin expression. In addition, we showed that all the alterations noted in the skin of diabetic rats were sensitive to treatment with insulin, indicating a direct correlation with the diabetic state.